Class Opt

tutorials/external/catch.hpp:7482–7581

    }

    class Opt : public ParserRefImpl<Opt> {
    protected:
        std::vector<std::string> m_optNames;

    public:
        template<typename LambdaT>
        explicit Opt( LambdaT const &ref ) : ParserRefImpl( std::make_shared<BoundFlagLambda<LambdaT>>( ref ) ) {}

        explicit Opt( bool &ref ) : ParserRefImpl( std::make_shared<BoundFlagRef>( ref ) ) {}

        template<typename LambdaT>
        Opt( LambdaT const &ref, std::string const &hint ) : ParserRefImpl( ref, hint ) {}

        template<typename T>
        Opt( T &ref, std::string const &hint ) : ParserRefImpl( ref, hint ) {}

        auto operator[]( std::string const &optName ) -> Opt & {
            m_optNames.push_back( optName );
            return *this;
        }

        auto getHelpColumns() const -> std::vector<HelpColumns> {
            std::ostringstream oss;
            bool first = true;
            for( auto const &opt : m_optNames ) {
                if (first)
                    first = false;
                else
                    oss << ", ";
                oss << opt;
            }
            if( !m_hint.empty() )
                oss << " <" << m_hint << ">";
            return { { oss.str(), m_description } };
        }

        auto isMatch( std::string const &optToken ) const -> bool {
            auto normalisedToken = normaliseOpt( optToken );
            for( auto const &name : m_optNames ) {
                if( normaliseOpt( name ) == normalisedToken )
                    return true;
            }
            return false;
        }

        using ParserBase::parse;

        auto parse( std::string const&, TokenStream const &tokens ) const -> InternalParseResult override {
            auto validationResult = validate();
            if( !validationResult )
                return InternalParseResult( validationResult );

            auto remainingTokens = tokens;
            if( remainingTokens && remainingTokens->type == TokenType::Option ) {
                auto const &token = *remainingTokens;
                if( isMatch(token.token ) ) {
                    if( m_ref->isFlag() ) {
                        auto flagRef = static_cast<detail::BoundFlagRefBase*>( m_ref.get() );